<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 7. 实现trim(str)方法，过滤字符串首位空白 -->
    <script>
        var str =" hello JavaScript "
        var str1 = str.trim();
        console.log(str1)
        console.log(str)
    </script>
</body>
</html>